The present invention generally relates to hybrid semiconductor assemblies that incorporate at least two dissimilar semiconductor devices. More specifically, the present invention relates to hybrid semiconductor modules incorporating at least one optoelectronic device and at least one electronic circuit (e.g. CMOS), methods for making the hybrid modules, and optoelectronic switching and interconnect assemblies incorporating the hybrid modules.
Electronic circuits fabricated in silicon form the foundation of modern technology for communication and computing. Technologies for building optoelectronic devices such as semiconductor lasers and detectors as well as electrooptic modulators have advanced to a point where such devices are becoming major components of high performance communication and computing systems. It would be desirable to combine both the silicon electronic and the optoelectronic/electrooptic devices in a single unit in order to lower the cost as well as reduce the power and speed penalty incurred when these two devices are deployed in separately packaged units.
The vertical cavity surface-emitting laser (VCSEL) is an example of an optoelectronic device desirably integrated with CMOS circuitry. The VCSEL has emerged as a new light source alongside the conventional edge-emitting semiconductor laser. Advantages of the VCSEL include its compactness, inherent single-longitudinal mode operation, circular beam profile, low current threshold (as low as 20 xcexcA), low power dissipation, and potential for integration with other electronic circuitry. Vertical-cavity lasers hold promise of superior performance in many optoelectronic applications and lower manufacturing cost than edge-emitting lasers. VCSELs are excellent light sources for optical data links. VCSELs are processed and tested at the wafer level, and one-dimensional or two dimensional arrays suitable for coupling to fiber optic ribbons or matrices are readily fabricated. Light is emitted perpendicular to the substrate with a circular beam that enables efficient, direct fiber or waveguide coupling. Particularly desirable are VCSELs emitting light of wavelength approximately 850-nm. Such VCSELs may be fabricated in high yield and are commercially available (e.g., Emcore Corp. MODE Division, Albuquerque, N.Mex.).
Furthermore, two-dimensional arrays of VCSELs can be imaged in free space using lenses or transmitted in two dimensional bundles of fibers (image guide) in order to implement optical interconnects, for example, highly parallel (thousands of channels) optical data links. Such applications have been analyzed theoretically (e.g., Louderback, et al., xe2x80x9cModulation and Free-Space Link Characteristics of Monolithically Integrated Vertical-Cavity Lasers and Photodetectors with Microlensesxe2x80x9d, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 2, March/April 1999, pp. 157-165; Simonis, et al., xe2x80x9cResearch on VCSEL interconnects and OE processing at Army Research Laboratoryxe2x80x9d, Proc. SPIE, 3946, paper #28, SPIE Photonics West, San Jose, Calif., Jan. 22-28, 2000).
Metal-oxide semiconductor (MOS) technology is virtually the standard for digital circuits that are used for computers and telecommunications. Increasingly, CMOS (complementary MOS) technology is utilized in these applications. CMOS technology incorporates both n-channel MOS and p-channel MOS transistors in the same monolithic structure. No other approach can compare with the high device densities and high yields available with silicon CMOS technology.
High-density CMOS electronic circuits are typically made in silicon, while high performance optoelectronic devices are typically made in various optically active materials, such as compound semiconductors, most commonly III-V materials, especially GaAs, as well as II-VI semiconductors such as ZnSe, transparent ferroelectrics such as lithium niobate and other related oxide materials, and liquid crystal and other optoelectronic polymers.
Optoelectronic devices may be fabricated in epitaxial layers grown on suitable substrates which are not ordinarily silicon. For example, VCSELs are typically fabricated in AlGaAs and GaAs on GaAs substrates. Optoelectronic devices may also be fabricated in single crystal materials such as oxides.
Thus, it is necessary to find methods to combine the high density, high speed CMOS devices (typically made in silicon) with the optoelectronic devices (typically made in III-V materials) in an intimate fashion in order to minimize parasitic capacitance and inductance and to increase density of optical interconnects. Applications for such a capability include chip-to-chip communication through formation of transmitter, receiver and/or amplifier modules for optical fiber communication.
One approach to integrate Si and III-V materials is heteroepitaxial growth, that is the crystalline growth of one material on a dissimilar crystal substrate. Heteroepitaxial growth of GaAs on silicon, and silicon on GaAs have been explored. After decades of research, fundamental problems such as the mismatch in the crystal lattice constants and the difference in the coefficients of thermal expansion of the two materials have prevented this goal from being satisfactorily achieved. The limitations are particularly acute when high performance lasers, photodetectors or drive electronics are required.
Another approach is called epoxy casting, by which completely fabricated chips are mounted in a common epoxy cast and final metal deposited. This is a form of manufacturing commonly called multi-chip modules, or MCMs. This approach also has numerous problems, including high cost and poor parasitics, size, reliability and yield.
More recently, several approaches have been investigated that are based on a technique of flip-chip bonding. In this technique, a chip is flipped over and attached to a substrate or other chip by a solder joint. Hence, two dissimilar chips are brought into intimate electrical and mechanical contact with each other. For example, the flip-chip bonding technique has been used for combining low temperature long-wavelength infrared (IR) detector arrays with silicon readout circuitry. There are commercial machines that can perform this flip-chip bonding operation with great reliability and repeatability. For long-wavelength infrared (IR) detector arrays, the detector array substrate may be transparent to the infrared wavelengths being detected by the IR detector array, thus facilitating the optical coupling to a flip-chip mounted IR detector. However, for optical wavelengths less than approximately 1 xcexcm, the detector substrate is often too opaque for use as a transparent substrate, so this technique cannot be used and hence the substrate needs to be removed for optical access to the OE devices.
Individual steps typically involved in heterogeneous bonding of OE devices may include the following:
1. Process the appropriate wafers to build electronic and optoelectronic devices;
2. Test, then separate out functional devices;
3. Interconnect electronic and optoelectronic devices by wire bonding, solder, flip-chip bonding, wafer bonding, etc.; and
4. Remove any substrates necessary to provide optical access to the optoelectronic device.
The order in which these operations are performed is often varied; and there are multiple variations on how to accomplish each step or series of steps. In one variation, the optoelectronics circuits are separated from their GaAs substrate as a very thin layer, then applied to a new substrate as a decal. This technique is very expensive and has numerous limitations on speed and design.
In a second variation, two wafers are bonded together and the backside of one of the wafers is removed by grinding and etching. Thickness control of the silicon film is difficult, and the cost is high. This technique is not suitable for attachment of a Si wafer to GaAs wafer due to the brittleness of GaAs.
In yet another variation, known good die of electronics and OE devices can each be assembled by flip-chip attaching them to a common transparent substrate on which interconnect wiring has been defined. This technique has the advantage that an ideal optical substrate such as sapphire can be used to combine electronics with optical components and permit the light to emit through the substrate. However, the silicon electronics exhibits high internal parasitic capacitance and crosstalk and the assembly becomes an expensive form of a multi-chip module, with all the limitations and costs of that approach. Furthermore, the interconnect wiring on the transparent substrate has significant amounts of parasitic capacitance and inductance which cause a loss of performance.
The opacity of the substrate material (GaAs or Si) to the optical radiation at the often-preferred wavelengths of 850-nm and less presents a significant obstacle to easy hybrid integration of electronic (CMOS) and optoelectronic devices. An additional major issue is that the electronics and optoelectronic devices generate heat, which must be removed to maintain all device performance and reliability characteristics. Also, GaAs is a very brittle material and the devices are sensitive to stress.
U.S. Pat. No. 5,858,814 (xe2x80x9cHybrid Chip and Method Thereforxe2x80x9d) discloses a method for co-locating on a common semiconductor substrate two or more different types of GaAs-based or InP-based optoelectronic components, such as a p-i-n diode and a surface-emitting laser, or a quantum well modulator. The common substrate is a silicon wafer which includes electronic circuitry to control the optoelectronic elements. The optoelectronic components have different epitaxial structures and may be grown on different substrates, e.g., GaAs or InP. Due to the opacity of the silicon and III-V substrates, the optoelectronic devices must each be fabricated with an etch-stop stop layer, and after each is bonded to the common silicon substrate, its original III-V substrate is etched away, in order to provide optical access to the device.
U.S. Pat. No. 5,923,951 (xe2x80x9cMethod of Making a Flip-Chip Bonded GaAs-Based Opto-Electronic Devicexe2x80x9d) describes GaAs-based optoelectronic devices flip-chip bonded to a silicon substrate bearing microelectronic circuitry for controlling the optoelectronic elements. A method to facilitate removal of the GaAs substrate in order to provide optical access to the optoelectronic elements using etch stop layers and selective etching is disclosed.
U.S. Pat. No. 6,005,262 (xe2x80x9cFlip-Chip Bonded VCSEL CMOS Circuit with Silicon Monitor Detectorxe2x80x9d) describes a hybrid chip wherein the VCSEL is provided with a blocking layer, e.g., aluminum to prevent rearwardly emitted photons from the VCSEL for interfering CMOS operation. The VCSEL is configured to emit light from a first surface of the device, but a problem arises in that a significant amount of light is also emitted in the anti-parallel direction, through a second surface of the device into the substrate. The light emitted through the second surface of the VCSEL may be absorbed by the silicon CMOS circuitry, degrading its performance. The blocking layer addresses that problem. In another embodiment, the blocking layer is removed and a photon detector is formed in the CMOS for collecting the rearwardly emitted photons for use in determining, inter alia, VCSEL power.
Lin, et al., (xe2x80x9cHigh-Performance Wafer-Bonded Bottom-Emitting 850-nm VCSEL""s on Undoped GaP and Sapphire Substratesxe2x80x9d, IEEE Photonics Technology Letters, Vol. 11, No. 12, December 1999, pp. 1542-1544) describe a GaAs VCSEL bonded to a sapphire substrate to provide a high-efficiency 850-nm bottom-emitting VCSEL. Flip-chip bonding of the bottom-emitting VCSEL with silicon circuitry provides hybrid integration of the VCSEL with the silicon circuitry. The 850-nm wavelength light from the bottom-emitting VCSEL passes through the sapphire substrate, not through the silicon circuitry or its substrate.
Louderback, et al. (xe2x80x9cFlip-Chip Bonded Arrays of Monolithically Integrated, Microlensed Vertical-Cavity Lasers and Resonant Photodetectorsxe2x80x9d, IEEE Photonics Technology Letters, Vol. 11, No. 3, March 1999, pp. 304-306) describe 980-nm bottom-emitting VCSELs bonded to semi-insulating GaAs substrates. At this wavelength, the GaAs is reasonably transparent to the VCSEL emission. However, the CMOS circuitry is on another substrate, presumably silicon, which is bonded to the VCSEL assembly. In this structure, light is transmitted through the GaAs substrate and does not pass through the CMOS circuitry substrate.
There is, therefore, a need for an improved commercially-viable method for assembling such differently configured optoelectronic and electronic devices such that hybrid chips incorporating such devices can be produced with minimal sacrifice in the performance of the devices.
The present invention describes devices (and methods for making such devices) which combine electronic and optoelectronic devices into a single integrated module that overcomes many of the disadvantages and shortcomings of previously described devices and methods. Furthermore, the present invention describes techniques which are readily manufacturable and that do not sacrifice the speed and power performance of either of the individual electronic or optoelectronic device components. The present invention includes a hybrid module and method for making the hybrid module which combines electronic devices (e.g. silicon CMOS devices and circuitry) with optoelectronic devices (e.g. GaAs lasers, detectors, etc.) in a manner which enables radio frequency electronic circuits, analog electronic circuits, digital electronic circuits, and optoelectronic devices to operate at high frequency without interfering with each other.
The present invention addresses some of the specific challenges and shortcomings previously described by using transparent, insulating substrate materials for integration of optoelectronic and electronic capabilities. Of such transparent, insulating materials, oxides such as sapphire and spinel are particularly desirable substrate materials for integrated electronic-optoelectronic modules. For example, sapphire is transparent to a very wide range of optical wavelengths and possesses excellent optical homogeneity; its coefficient of thermal expansion closely matches that of the GaAs used for many optoelectronic devices; and it is an excellent electrical insulator and thermal conductor.
Integration of silicon electronic devices/circuits with optoelectronic devices on a common insulating transparent substrate requires that an effective method for forming the silicon electronic devices/circuits on the transparent, insulating substrate be used. The present invention provides a method and structure for meeting this requirement in the form of a unique composite substrate comprising a monocrystalline semiconductor layer, such as silicon, epitaxially deposited on a supporting insulating substrate, such as sapphire. The advantages of using this type of composite substrate include the substantial reduction of parasitic capacitance between charged active regions in the silicon and the substrate and the effective elimination of leakage currents flowing between adjacent active devices. This is accomplished by employing as the substrate an insulating material, such as sapphire (Al2O3), spinel, or other known highly insulating materials, and providing that the conduction path of any interdevice leakage current must be through the insulating substrate.
An xe2x80x9cidealxe2x80x9d silicon-on-sapphire composite substrate may be defined to include a completely monocrystalline, defect-free silicon layer of sufficient thickness to accommodate the fabrication of active devices therein. In this xe2x80x9cidealxe2x80x9d silicon-on-sapphire composite substrate, the silicon layer is adjacent to a sapphire substrate and has a minimum of crystal lattice discontinuities at the silicon-sapphire interface. Early attempts to fabricate this xe2x80x9cidealxe2x80x9d silicon-on-sapphire composite substrate were frustrated by a number of significant problems, which can be summarized as (1) substantial incursion of contaminants into the epitaxially deposited silicon layer, especially the p-dopant aluminum, as a consequence of the high temperatures used in the initial epitaxial silicon deposition and the subsequent annealing of the silicon layer to reduce defects therein; and (2) poor crystalline quality of the epitaxial silicon layers when the problematic high temperatures were avoided or worked around through various implanting, annealing, and/or regrowth schemes.
It has been found that silicon on sapphire composite wafers/substrates having high quality silicon films suitable for demanding device applications can be fabricated on sapphire substrates by a method that involves: epitaxial deposition of a silicon layer on a sapphire substrate; implanting a given ion species into the silicon layer to form a buried amorphous region in the silicon layer which extends substantially from the surface of the sapphire substrate into the silicon layer, thus leaving a surface layer of monocrystalline silicon covering the buried amorphous region; and annealing the silicon on sapphire composite wafer to induce solid phase epitaxial regrowth of the buried amorphous region using the surface layer of monocrystalline silicon as a crystallization seed. The high quality of the silicon layer is preserved during device fabrication in the silicon layer by performing any processing which subjects the silicon layer to temperatures in excess of approximately 950xc2x0 C. in an oxidizing ambient environment, and performing any processing which subjects the silicon layer to temperatures which are less than approximately 950xc2x0 C. in either one of an oxidizing ambient environment or a non-oxidizing ambient environment.
Examples of devices and methods for making silicon-on-sapphire composite wafers/substrates and devices thereon are described in U.S. Pat. Nos. 5,416,043 (xe2x80x9cMinimum Charge FET Fabricated on an Ultrathin Silicon on Sapphire Waferxe2x80x9d); 5,492,857 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,572,040 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,596,205 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,600,169 (xe2x80x9cMinimum Charge FET Fabricated on an Ultrathin Silicon on Sapphire Waferxe2x80x9d); 5,663,570 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,861,336 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,863,823 (xe2x80x9cSelf-Aligned Edge Control in Silicon on Insulatorxe2x80x9d); 5,883,396 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d); 5,895,957 (xe2x80x9cMinimum Charge FET Fabricated on an Ultrathin Silicon on Sapphire Waferxe2x80x9d); 5,920,233 (xe2x80x9cPhase Locked Loop Including a Sampling Circuit for Reducing Spurious Side Bandsxe2x80x9d); 5,930,638 (xe2x80x9cMethod of Making a Low Parasitic Resistor on Ultrathin Silicon on Insulatorxe2x80x9d); 5,973,363 (xe2x80x9cCMOS Circuitry with Shortened P-channel Length on Ultrathin Silicon on Insulatorxe2x80x9d); 5,973,382 (xe2x80x9cCapacitor on Ultrathin Semiconductor on Insulatorxe2x80x9d); and 6,057,555 (xe2x80x9cHigh-Frequency Wireless Communication System on a Single Ultrathin Silicon on Sapphire Chipxe2x80x9d). The entirety of each of the above mentioned patents is hereby incorporated herein by reference. Additionally, all other patents, patent applications and other publications mentioned in this specification are hereby incorporated herein by reference in their entirety.
By the methods described in the patents listed above, electronic devices can be formed in an extremely thin layer of silicon on an insulating sapphire substrate. The thickness of the silicon layer is typically less than approximately 150-nm. This xe2x80x9cultrathinxe2x80x9d silicon layer maximizes the advantages of the insulating sapphire substrate and allows for the integration of multiple functions on a single chip. Traditional transistor isolation wells required when using traditional thick silicon structures and techniques are unnecessary, simplifying transistor processing and increasing device/circuit densities. These improved thin silicon on insulator methods and devices will be distinguished herein from earlier thick-silicon embodiments by referring to them collectively as xe2x80x9cultrathin silicon-on-sapphire.xe2x80x9d
Many types of circuitry, including CMOS circuits, have been fabricated in this ultrathin silicon-on-sapphire prepared by the methods referred to above. CMOS circuitry fabricated in ultrathin silicon-on-sapphire composite substrates exhibit very high speed and low power characteristics. While the ultrathin silicon-on-sapphire composite substrates have the advantage that well-known silicon circuit design and technology can be used to fabricate many devices in the thin silicon layer, further advantageous circuit designs are also possible that are uniquely enabled by the distinctive electrical and materials properties of the thin silicon layer on the sapphire substrate. For example, the present invention makes it possible for these well-known and further advantageous silicon circuits (fabricated in the ultrathin silicon-on-sapphire composite structure) to serve as the substrate/foundation upon which optoelectronic devices can be attached, thereby creating an integrated hybrid electronic-optoelectronic module. Optoelectronic devices which benefit by being integrated with silicon electronic circuitry (e.g. CMOS) based in composite substrates, such as the ultrathin silicon-on-sapphire, include all such devices that manipulate light, including but not limited to light-emitting diodes, lasers, photodetectors and modulators.
The devices and methods of the present invention utilize this ultrathin silicon-on-sapphire composite substrate to successfully integrate electronic devices (e.g. silicon CMOS devices and circuitry) with optoelectronic devices (e.g. GaAs lasers, detectors, etc.) into a hybrid module.
Applications of the present invention include electronic-optoelectronic modules and devices and methods for fabricating such modules and devices. In a first example, a first wafer having electronic circuits/devices thereon is wafer-level flip-chip bonded to a second wafer having optoelectronic devices thereon. The first wafer is an ultrathin silicon-on-sapphire composite substrate wafer which includes: 1) electronic devices; 2) optically transparent areas; and 3) bonding pads. The second wafer is a suitable substrate bearing the optoelectronic devices and bonding pads such that the bonding pads on the first and second wafers align appropriately. The wafer-level bonding is followed by dicing of the flip-chip bonded structure to yield hybrid integrated devices, each of which incorporates at least one optoelectronic device and at least one electronic circuit in electrical communication therewith.
In a second example, the present invention provides hybrid chips that can be used to form an improved optical interconnection system. Such an optical interconnection system includes an array of optical input waveguides for delivering a plurality of optical input signals to an array of input optoelectronic devices (detectors) on the hybrid chip. Logic circuitry on the chip processes electrical signals generated by the input optoelectronic devices and controls the output optoelectronic devices. The output optoelectronic devices generate a plurality of optical output signals which are delivered to an array of output waveguides.
In a third example, the present invention provides hybrid chips that can be used to form an improved optical interconnection system based on one-dimensional or two-dimensional arrays of optical beams propagating in free space or two-dimensional arrays of optical fiber interconnects.
In these examples, the electronic circuits in silicon may include CMOS devices. Typical CMOS devices include VCSEL drivers, receiver circuits for photodetectors, and other signal/data processing and switching circuits. Typical optoelectronic devices may include light-emitting devices such as lasers and diodes, light detecting devices such as photodetectors, and light modulators, such as quantum well modulators. Often, the light emitting optoelectronic devices are fabricated in III-V materials; and the light detecting devices are fabricated in III-V, IV and II-VI materials. For infrared and visible light, the light emitting devices are commonly on GaAs substrates and light detecting devices are fabricated in GaAs, InGaAs, Si, Ge. In the practice of the present invention, it is an advantage that optoelectronic devices of more than one type of material may be incorporated into the hybrid module. For example, an advantageous combination comprises a II-VI based photodetector input, fabricated for example in HgCdTe, as input, in combination with a III-V based VCSEL output, fabricated for example in GaAs.
In a first aspect, the present invention is an integrated electronic-optoelectronic module comprising: a composite substrate comprising a thin layer of silicon on a transparent, insulating substrate; at least one electronic device fabricated in the thin layer of silicon; and at least one optoelectronic device bonded to the composite substrate and in electrical communication with at least one electronic device fabricated in the thin layer of silicon. The optoelectronic device may be selected from lasers, light-emitting diodes, photodetectors, and modulators. The laser may further include a vertical cavity surface-emitting laser (VCSEL). The at least one electronic device may further include a CMOS electronic circuit for driving a VCSEL or an amplifier for the photodetector. In some configurations, the transparent, insulating substrate comprises sapphire.
In a second aspect, the present invention is an integrated electronic-optoelectronic module comprising: an ultrathin silicon-on-sapphire composite substrate; at least one electronic device fabricated in the ultrathin silicon; and at least one optoelectronic device bonded to the ultrathin silicon-on-sapphire composite substrate and in electrical communication with the at least one electronic device fabricated in the ultrathin silicon. The optoelectronic device may be selected from lasers, light-emitting diodes, photodetectors, and modulators. The laser may further include a vertical cavity surface-emitting laser (VCSEL). The at least one electronic device may further include a CMOS electronic circuit for driving a VCSEL or an amplifier for the photodetector.
In a third aspect, the present invention is a method for making an integrated electronic-optoelectronic module comprising the steps of: providing an ultrathin silicon-on-sapphire composite substrate having a main upper surface comprising a silicon layer; fabricating one or more electronic circuits in the silicon layer, including one or more bonding pad(s) in electrical contact with the one or more electronic circuits and arranged in a predetermined spaced-apart array; forming one or more optically transparent areas in the silicon layer correspondingly adjacent to the one or more electronic circuits; dicing the ultrathin silicon-on-sapphire composite substrate bearing the electronic devices, bonding pad(s), and optically transparent areas, to yield individual silicon-on-sapphire die each of which bears one or more electronic device, bonding pad, and optically transparent area; fabricating one or more optoelectronic devices on a suitable substrate, including one or more bonding pad(s) in electrical contact with the one or more optoelectronic devices and arranged in a predetermined spaced-apart array that matingly corresponds with the predetermined spaced-apart array of bonding pad(s) formed in the silicon-on-sapphire composite substrate; dicing the suitable substrate bearing the optoelectronic devices and bonding pad(s) to yield individual optoelectronic die, each of which bears one or more optoelectronic device and bonding pad; and combining the silicon-on-sapphire die with the optoelectronic die via their respective bonding pads by the technique of flip-chip bonding, to yield an integrated optoelectronic module. In some configurations, the suitable substrate for the optoelectronic device is a III-V material, e.g., GaAs. The optoelectronic device may be selected from lasers, light-emitting diodes, photodetectors, and modulators. The laser may further include a vertical cavity surface-emitting laser (VCSEL). The at least one electronic device may further include a CMOS electronic circuit for driving a VCSEL or an amplifier for amplifying a signal from the photodetector.
In a fourth aspect, the present invention is a method for making an integrated electronic-optoelectronic module comprising the steps of: providing an ultrathin silicon-on-sapphire composite substrate wafer having a main upper surface comprising a silicon layer; fabricating one or more electronic circuits in the silicon layer, including one or more bonding pad(s) in electrical contact with the one or more electronic circuits and arranged in a predetermined spaced-apart array; forming one or more optically transparent areas in the silicon layer correspondingly adjacent to the one or more electronic circuits; and fabricating one or more optoelectronic devices on a suitable substrate wafer, including one or more bonding pad(s) in electrical contact with the one or more optoelectronic devices and arranged in a predetermined spaced-apart array that matingly corresponds with the predetermined spaced-apart array of bonding pad(s) formed in the silicon-on-sapphire composite substrate wafer; and combining the electronic circuits on the silicon-on-sapphire composite substrate wafer with the optoelectronic devices on the suitable substrate wafer via their respective bonding pads by the technique of flip-chip bonding to yield a bonded structure; and dicing the bonded structure to yield hybrid integrated devices, each of which incorporates at least one optoelectronic device and at least one electronic circuit in electrical communication therewith.
In a fifth aspect, the present invention is an integrated electronic-optoelectronic interconnection comprising: an array in a first pattern of vertical-cavity surface emitting lasers formed on a first planar surface of a first suitable substrate, for generating output radiation at a desired wavelength of operation, said radiation being emitted orthogonal to and mainly directed into said first planar surface; an array in a second pattern of photodetectors formed on a second planar surface of a second suitable substrate, for detecting input radiation at a desired wavelength of operation, said photodetectors detecting radiation received on the second planar surface; an ultrathin silicon-on-sapphire composite substrate having a third planar surface bearing electronic circuitry for processing electrical signals generated by the input radiation to the photodetectors and controlling the output radiation of the vertical-cavity surface emitting lasers, wherein the ultrathin silicon-on-sapphire composite substrate is provided with optically transparent areas; and electrical contacts formed by flip-chip bonding the first and second planar surfaces to the third planar surface, electrically connecting the vertical-cavity surface emitting lasers formed on the first suitable substrate, the photodetectors formed on the second suitable substrate, and the electronic circuitry for processing electrical signals generated by the input radiation to the photodetectors and controlling the output vertical-cavity surface emitting lasers; wherein said electrical contacts being formed so that the first array of vertical cavity surface-emitting lasers and the second array of photodetectors respectively emit output radiation or detect input radiation through the optically transparent areas of the ultrathin silicon-on-sapphire composite substrate.
In a sixth aspect, the present invention is a method for fabricating an electronic-optoelectronic module comprising: providing a composite substrate comprising a thin layer of silicon on a transparent, insulating substrate, having a main upper surface comprising the thin layer of silicon; fabricating one or more electronic circuits in the thin layer of silicon using well-known micro-fabrication techniques, including one or more bonding pads in a pre-determined spaced-apart pattern, each in electrical communication with the one or more electronic circuits; forming one or more optically transparent areas in the thin layer of silicon correspondingly adjacent to the one or more electronic circuits; dicing the composite substrate bearing the electronic devices, the optically transparent areas, and the bonding pads to yield individual composite die each of which bears one or more electronic device, optically transparent area, and bonding pad in a pre-determined spaced-apart pattern in electrical communication with the electronic device; fabricating one or more optoelectronic devices on a suitable substrate including one or more bonding pads in a pre-determined spaced-apart pattern, each in electrical communication with one or more optoelectronic devices; providing bonding pads on the suitable substrate correspondingly adjacent to and in electrical communication with the one or more optoelectronic devices; dicing the suitable substrate bearing the optoelectronic devices and bonding pads to yield individual optoelectronic die each of which bears one or more optoelectronic device and bonding pads; and combining the composite substrate die with the optoelectronic die via the bonding pads by the technique of flip-chip bonding to yield an integrated optoelectronic module. In some configurations, the transparent, insulating substrate comprises sapphire.